Interventional imaging is the use of magnetic resonance imaging (MRI) of a subject during remedial action upon the subject. MR images are used to monitor the progress, success and problems that occur during the remedial action.
Interventional medical imaging is the practice of MRI of a patient during medical treatment of the patient to monitor the progress, success and problems that occur during the medical treatment. Interventional imaging is used in emergency and non-emergency situations. Examples of non-emergency interventional imaging include MRI-guided biopsy, MRI-guided surgery, dynamic musculoskeletal MRI, MRI-guided minimally invasive thermal therapies, MRI-guided vascular interventions, and fluoroscopy.
In interventional imaging, the MR image is generated continuously, or intermittently at regular or irregular intervals, or on an ad-hoc basis.
However, medical interventional imaging often requires the use of surgical equipment. The surgical equipment includes electronic medical diagnostic equipment or electronic medical monitoring equipment, such as a surgical microscope and patient monitoring equipment. However, the strong magnetic stray field of a MRI system often interferes with the operation of the additional equipment within a certain range of the MRI system. Surgical equipment is operated outside of the range. In one example an MRI system must not generate a magnetic field above five gauss beyond a range of four meters from the center of an MRI magnet of the MRI system in order to accommodate operation of other electrical medical equipment 4 meters from the MRI system.
Operating the surgical equipment outside of the range of electromagnetic interference of an MRI system is at the very least, inconvenient for the technicians and healthcare providers involved in the use of the additional equipment. The inconvenience results in a loss of productivity of the technicians and healthcare providers. In more serious situations, the inconvenience can yield poor communication between the technicians and healthcare providers that can result in less than optimal healthcare for the patient.
More specifically, conventional interventional MRI systems comprise two basic types of systems, open MRI systems with interventional access and cylindrical MRI systems with movement of patient.
In regards to open MRI systems with interventional access, the open MRI systems typically have lower magnetic stray field with lower imaging capability. This type of MRI system allows real-time intervention at some limited surgeon access. Other open MRI systems have higher magnetic stray field strength and increased access, but these systems also have larger stray fields. The larger stray field limits access by technicians and healthcare providers to required surgical equipment such as microscopes, patient monitoring equipment, etc.
In regards to cylindrical systems with movement of patient, these systems can be used for interventional procedures by removing patients from high magnetic stray field region for surgery and replacing patient in cylindrical system to verify interventional procedures. However this presently requires motion of the patient by a considerable distance to move patient to a region of low magnetic stray field strength. In the conventional cylindrical MRI systems, the 5 gauss line is located 4 meters from magnet isocenter along the patient axis. Thus, moving the patient to a region of low magnetic stray field strength typically requires motion of table away from the system and increases possibility of registration and/or misalignment of patient with imaging system.
In general, cylindrical MRI systems are more attractive for their higher imaging capability, inherent high signal to noise ratio imaging speed and wide range of pulse sequences available. Cylindrical systems can be used for interventional procedures by inserting catheters while the patient is out of the magnet, then manipulating the catheters while the patient is in magnet. However, again the high field region extends a considerable distance from the magnet, with 5 Gauss regions typically 4 meters axially and 2.5 meters radially. This limits placement of some equipment in close to the magnet.
An increasingly popular technique used in interventional procedures, is imaging fusion. Imaging fusion is a combined use of MR and X-ray imaging. Since these two imaging systems are typically installed in separate rooms, the patient has to be transported significant distance increasing the chance for mis-registration and the time for the procedure. Today, most hospitals that are using high field cylindrical magnet MRI systems for surgery, either to perform the imaging and surgery in separate rooms, requiring significant patient travel, or to perform the imaging and surgery in a very large room to allow the patient to be moved to a region outside the 5 Gauss field, where standard surgery equipment and tools can be operated.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art to place and operate interventional medical equipment such as electronic medical diagnostic equipment or electronic medical monitoring equipment in close proximity to a MRI system.